Impact of organic residues and mineral fertilizer application on soil–crop systems I: yield and nutrients content

A five-season experiment was initiated to study the effects of the recycling of some organic residues on a soil–crop system of a guar–wheat rotation in a sandy clay loam soil located in the semi-arid tropics of Sudan. Treatments included: incorporation of crop residues alone after harvest (Cr⁺), with (FCr⁺) or without (FCr^?) inorganic fertilizer, sewage sludge (SS) and humentos (H). Grain yield of wheat in FCr⁺ and Cr⁺ treatments was significantly higher than that obtained in FCr^? and control plots by ～22?62% and 116?119%, respectively. When crop residues were incorporated with inorganic fertilizer, the priming effect of crop residues on straw yield (106%) was almost double that of the priming effect of inorganic fertilizer (56%). The sustainable yield index of wheat straw dry matter for the control, crop residue, humentos, inorganic fertilizer, combined fertilizer and crop residue and sewage sludge was 28, 27, 8, 35, 21 and 38%, respectively. In general, N, P and K of straw dry matter (SDM) was in the order of FCr⁺ > FCr^? > SS > Cr⁺> H > C. The findings suggest that repeated incorporation of crop residues with inorganic fertilizer and applications of SS could both sustain wheat performance in the dryland ecosystems.     

The “conuco”—an important refuge of Cuban plant genetic resources

Summary The conuco in Cuba is a large garden or a small field where agriculture is practiced in a traditional way. The history of the conuco is discussed. Composition and structure of actual conucos are described on the basis of four cases studied in Eastern Cuba. Their cultivated plants came from nearly all regions of diversity of the world. The crops from the Central American and Mexican region are most important. The great diversity of different crops as well as the marked variation within most of the cultivated plants stress the importance of the conuco as a reservoir for plant genetic resources.

---

Der Conuco — ein bedeutendes Reservoir für pflanzliche genetische Ressourcen in Kuba

Zusammenfassung Der kubanische Conuco ist ein größerer Garten oder ein kleineres Feld mit traditioneller landwirtschaftlicher Produktion. Die Geschichte des Conuco wird diskutiert. Zusammensetzung und Struktur aktueller Conucos werden auf der Grundlage von vier ostkubanischen ausgewählten Fallbeispielen beschrieben. Ihre Kulturpflanzen stammen beinahe aus allen Mannigfaltigkeitszentren der Welt. Besonders bedeutsam sind die Kulturpflanzen der mittelamerikanischen und mexikanischen Region. Die große Mannigfaltigkeit unterschiedlicher Fruchtarten und die ausgeprägte infraspezifische Variabilität bei den meisten Kulturpflanzen unterstreichen die Bedeutung des Conuco als Reservoir für pflanzliche genetische Ressourcen.

---

—

— . . 4- , . - . - . .

     

Switchgrass from North Dakota – an adaptable and promising energy crop for northern regions of Europe

Searching for novel energy crops, an interest in C4-type plant switchgrass (SWG) has increased worldwide. The present research was aimed to study SWG genetic resources for most important agrobiological traits with a view of extending the range of energy plants in the Nemoral zone of Europe. SWG was studied for the peculiarities of developmental stages, winter hardiness, and dry matter (DM) yield. SWG regrowth in spring started one month later compared to the reed canary grass (variety ‘Chiefton’). All investigated genotypes matured seeds in the second half of September. The most winter-hardy SWG accessions (0–20% winter damage) were the majority of wild ecotypes and the variety ‘Dacotah’ from North Dakota (2–4 hardiness zone) as well as the variety ‘Summer’ from South Nebraska (4, 5 hardiness zone). Ecotypes from North Dakota exhibited a high breeding potential and prospects in Northern regions of Europe due to genotypic variation of winter hardiness trait. The varieties ‘Alamo’, ‘Falcon’, ‘Grenville’, ‘Shawnee’, and ‘Trailblazer’ that originated from warmer climate zones (6–9 hardiness zone) were heavily damaged or completely killed. The worst overwinter survival of plants was recorded after the first winter. DM yield was estimated at two regimens of cutting. When grass was cut once at seed maturity stage, DM yield in the first harvest year was 249 g per plant, in the second harvest year 349 g per plant, and in the third harvest year 493 g per plant. When grass was cut twice per season (at the beginning of anthesis and after regrowth of aftermath), DM yield was significantly lower: in the first harvest year the DM yield was 203 g per plant (18.4% less), in the second harvest year 182 g per plant (47.9% less), and in the third harvest year 272 g per plant (44.7% less).     

Assessment of plant nutrients’ dynamics in organically and conventionally managed soils by means of different extraction methods

The aim of this study was to investigate what kind changes in the soil fertility parameters occur depending on different farming methods. The field experiment was performed on sandy loam Luvisol during 2008–2014. The following treatments were carried out: organic (ORG), organic with farmyard cattle manure (ORGFYM) and conventional with farmyard cattle manure and mineral fertilizers (CONFYM). Soil samples were collected yearly in September and analyzed for P, K, Mg and Ca by the Mehlich III method. In parallel, ammonium lactate extractable P and K (AL method), and ammonium acetate extractable Mg and Ca (NH₄OAc-method) were determined. The Pearson correlation coefficients between the analysis results achieved by the Mehlich III method and alternative methods were calculated. In all the treatments, no significant changes in soil Corg content were established over seven years. A significant (p?AL in the soil but considerable decrease in the soil K_AL content was revealed. The application of cattle manure (60?t?ha^?1 for the 5-year crop rotation) in both organic and conventional treatments sustained the status of available nutrients in the soil. The Pearson correlation coefficients between Mehlich III and AL methods for P (r?=?0.770, p?r?=?0.922, p?4OAc-methods was found in the case of Mg (r?=?0.951, p?r?=?0.841, p?Mehlich III/P_AL quotient was inversely proportional with the Ca_{Mehlich III} values.     

Effects of copper on the decomposition of plant residues,microbial biomass,and β-glucosidase activity in soils

Abstract

Two types of soils (Brown Lowland soil and Ando soil), which were artificially enriched with different amounts of Cu, were incubated with or without pulverized orchard grass for 12 weeks at 25°C. For both soils with and without orchard grass amendment, the amount of CO₂ evolved over the 12-week period of incubation decreased by the enrichment with Cu at a concentration exceeding 1,000 mg kg^?1 soil. The decrease of the mineralization of added orchard grass in the Cu-enriched soil was conspicuous especially during the initial period of incubation. The amount of microbial biomass C at the end of the incubation was significantly reduced by the Cu enrichment regardless of the amendment with orchard grass. The relative decrease of the soil microbial biomass was much greater than that of the soil respiration. The amount of biomass C was negatively correlated with the amount of 0.1 M CaCl₂-extractable Cu as a logarithmic function. On the other hand, the β-glucosidase activity at the end of the incubation was not significantly affected by the presence of Cu in the soils without orchard grass amendment and increased with the increase in the amount of enriched Cu in the orchard grass-amended soils.     

Evaluation of an anion‐exchange membrane for extracting plant available phosphorus in soils

Abstract

Anion‐exchange resins (AER) have been used to determine plant available phosphorus (P) since the fifties and their results have shown strong relationships with plant growth and P uptake irrespective of soil properties. However, this procedure is still not widely used by laboratories because of difficulties in handling resin beads under routine conditions. New kinds and different shapes of resins are being produced each with specific characteristics that must be evaluated before use in laboratory procedures. Thus the objective of this work was to evaluate an AER manufactured in membranes reinforced with a Modacrylic fabric. These anion‐exchange membrane (AEM) sheets are commercially available, making them suitable for soil testing. The membranes were cut in pieces (1.0×7.5 cm) identified as AEM‐strips. The AEM‐strips were soaked in 0.5M HCl for a few days and transferred, after being rinsed with deionized water (DI), to 0.5M NaHCO₃ to convert them to HCO₃ ^‐ form. The AEM‐strips and resin beads in nylon bags recovered 98.4 and 98.0% of the P content in an aqueous P solution, respectively. Three eluent solutions were evaluated with different shaking times. The 0.1M H₂SO₄ and 1.0M NaCl in 0.1M HCl were equally suitable for the molybdenum blue color development without any pH adjustment, while the pH of the 0.5M HCl was too low. The elution of P from the AEM‐strips was independent of time with a 15‐min shaking being adequate for removal of all P from the strips. A comparison of soil sample preparation demonstrated that it was not necessary to vigorously grind or sieve the soil to improve the repeatability of the results. The AEM‐strips were compared with other methods (Pi impregnated filter paper, Mehlich I and Bray 1) using 32 soils from Guatemala with widely varying physico‐chemical and mineralogical properties. Phosphorus extracted by the AEM and Pi procedures (similar principle) were highly correlated and gave similar results irrespective of soil type. The acid extraction (Mehlich I and Bray 1 methods) attacked soil components (apatites) resulting in higher and inconsistent amounts of P extracted which may not be available to plants; the correlation between these methods within soils of similar properties was good, but when all soils were considered together the relationship was not significant. This demonstrated that the acid extraction method for P is not suitable for soils containing apatites, while those based on a sink for P (AEM and Pi) can be applied irrespective of the type of soil.     

Do railway edges provide functional connectivity for plant communities in an urban context?

Functional connectivity is essential to maintaining biodiversity in fragmented landscapes but little attention has been given to structures that can provide it in an urban context. Using both the taxonomic and functional diversity of semi-natural grassland plant communities, we assessed the functional connectivity of linear transportation infrastructures in urban landscape. We sampled the vegetation at 71 study sites located along the edges of two railway lines. We hypothesised that if railways favour functional connectivity, then spatially connected communities should be more similar than disconnected communities. Therefore, we compared floristic dissimilarities between site pairs that were either connected or separated by a railway spatial break (overpass or station). As a further approach, we supposed that functional connectivity may attenuate the effect of urbanisation filters on plant communities. Thus we examined whether and how edges’ plant communities were influenced by urbanisation and compared our results to the patterns described in the literature. Functional connectivity was mainly maintained at railway stations, contrary to overpasses, which seemed to interrupt dispersal, demonstrating that railway edges provide connectivity for some but not all functional groups: this was only true for moderately mobile species. Surprisingly, railway edges did not seem to play an additional connective function for invasive species, the presence of which being strongly related to the urbanisation intensity and not influenced by spatial breaks along railways. Our study thus highlights the potential function of railway edges as corridors for common grassland plants. Landscape managers should include railways in green networks to improve connectivity in urban landscapes.     

Self-generated microbial population or cultured microflora – an important criterion toward development of an effective and economically viable road map for organic soil management

Huge depletion of soil microflora under conventional farming practice has become the primary contributory factor toward the present depletion of soil and crop productivity. Reconstitution of soil microbial dynamics has been identified as the only way out, but there has been a debate regarding the most effective pathway for soil rejuvenation i.e. whether to create the environment for natural proliferation or opt for inoculation of laboratory generated microbes. In this respect, a study was undertaken at Maud T.E. (Assam) under FAO-CFC-TBI Project, where bio-fertilizer (microbial inoculant, MI), vermicompost (organic food source, OF), vermicompost + bio-fertilizer (OF+MI), and Novcom compost (representing self-generated native microflora in the order of 10¹⁶c.f.u. along with organic food source, SNM); were taken as treatments for a yield target of 1500 kg made tea/ha. The highest crop yield (1500 kg ha^?1) along with high and consistent soil quality development was noted under SNM treatment; while MI influenced lowest yield (1268 kg ha^?1) and minimal soil response. Addition of the organic food source with cultured microbes (MI+OF) was found to improve crop performance (1427 kg ha^?1), but with 7.60 times higher cost (Rs. 39.97 kg^?1 made tea). Economic viability study indicated that except SNM, all other treatments were vulnerable toward crop loss or market downfall.     

Reducing residues of tetracycline and its resistance genes in soil-maize system and improving plant growth:Selecting the best remediation substance

Tetracycline(TC)and tetracycline resistance genes(TRGs)in plant edible tissues pose a potential risk to the environment and then to human health.This study used a pot experiment to investigate the effects of different remediation substances(worm castings,fungal chaff,microbial inoculum,and biochar)on the physiological characteristics of maize and the residues of TC and TRGs in the soil-maize system under TC stress.The results showed that TC significantly inhibited growth,disrupted the antioxidant defense system balance,and increased proline and malondialdehyde contents of maize plants.Tetracycline residue contents were significantly higher in root than in shoot,and followed the order root>stem-leaf>grain,which was consistent with the distribution of bioconcentration factors in the different organs of maize plants.The TC residue content in the soil under different treatments was 0.013–1.341 mg kg-1.The relative abundances of different antibiotic resistance genes in the soil-maize system varied greatly,and in maize plants followed the order intI1>tetW>tetG>tet B>tetM>tetX>tetO.In the soil,tetX had the highest relative abundance,followed by tetG and tetW.A redundancy analysis(RDA)showed that TC was positively correlated with TRGs.The addition of different remediation substances alleviated the toxicity of TC on maize physiological characteristics and reduced the TC and TRG residues in the soil-maize system,with biochar being the best remediation substance.These results provide new insights into the effect of biochar on the migration of TC and TRGs from soil to plants.     

Soil phosphorus pools in the detritusphere of plant residues with different C/P ratio—influence of drying and rewetting

Little is known about the effect of drying and rewetting (DRW) on phosphorus (P) pools in the detritusphere, the soil adjacent to plant residues. Two plant residues differing in their potential to release P during decomposition were used: mature barley straw, C/P 255 or young faba bean, C/P 38. Residues were placed between two PVC caps filled with soil at 50% water-holding capacity with open ends covered by fine mesh onto which the residues were placed. The open ends of the two PVC caps were pressed together with residues in between. For the unamended controls, no residues were placed between the meshes. After 2 weeks incubation, the soil was separated from the residues and then either dried and kept dry for 2 weeks followed by rapid rewetting to 50% water-holding capacity (WHC) rewetting (RW) or maintained at 50% of WHC constantly moist (CM). Bioavailable P pools (readily available P pools: CaCl₂- and anion exchange-P; P bound to soil particles: citrate- and HCl-P; acid phosphomonoesterase- and microbial-P) were measured in dry soil and 1, 7, and 14 days after rewetting. Rewetting of dry soils induced a respiration flush on the first day after which respiration rates declined to those in CM. Compared to the unamended soil, the flush was about 75% higher with barley and more than twofold higher with faba bean. P pools were 3–20-fold higher with faba bean than with barley or in the control. At the end of the dry period, most P pools were higher in dry soil compared to CM. Rewetting had little effect on P pools 1, 7, and 14 days after rewetting compared to CM. To investigate if rewetting induced a short pulse of available P, a second experiment was carried out. As in the first experiment, faba bean detritusphere soil and control were generated and then dried or kept at 50% WHC for 2 weeks. Before rewetting, anion exchange membranes (AEM) were placed in the soil which were removed one, 2 or 4 days after rewetting. The P concentration on the AEM was more than threefold higher with faba bean than the control. One day after rewetting, the P concentration on the AEM with faba bean was about threefold higher in RW than in CM, but did not differ between RW and CM in the control. Four days after rewetting, nearly all P pools with faba bean were 10–30% lower in RW than in CM, except citrate-P which was about 5% higher in RW. We conclude that rewetting induces a short pulse of available P if the P pool concentration is high as in the detritusphere of faba bean. If P is removed from the soil (by binding to AEM or uptake by plants), rewetting can induce depletion of P pools compared to CM.     

Effects of fertilizer timing and placement on grain yield and leaf nutrients of sole‐crop cowpeas (V. unguiculata) in Sierra Leone

Abstract

Effects of fertilizer timing and placement on the grain yield and leaf nutrients of uninoculated sole‐crop cowpeas in two experiments during the minor cropping season on Njala upland soil of Sierra Leone were studied. Timing and placement and their interaction had no significant effects on grain yield. Placement affected highly significantly lamina Mg, Cu and Co and significantly lamina N and Ca. Placement and timing x placement interaction affected highly significantly petiole N and petiole P respectively. Timing affected highly significantly petiole N, which decreased as fertilizer application was delayed. The spectrum of nutrient distribution in both lamina and petiole was decidedly different. Multiple regression studies indicated that variability in only petiole Mg, Cu and Co significantly contributed to grain yield variability. By the introduction of 15 nutrients (6 lamina and 9 petiole) after examining the linear regression coefficients into a composite multiple regression study, lamina Ca, petiole Fe and petiole Co were selected as significant contributors to grain yield variability with marked improvement in R². Removal of the effects of the correlated variables produced significances in the effects of fertilizer placement and timing x placement interaction on grain yields.     

Shannon–Weaver index as an integrated indicator of metal differentiation in soil and plant samples

The degree of contrast (differentiation) in the distribution of metals in background and contaminated soils is one of the most important geochemical indicators. The Shannon–Weaver index (H) can be a suitable criterion for the distribution of metals in soil and plant samples. A procedure for calculating the Shannon–Weaver index is described. An index scale of five gradations, from no differentiation (H_rel = 1.0–0.9) to very high differentiation (H_rel = 0.3–0.1), is proposed. The background soils in different regions of Russia have low or even no differentiation of metals. Aerial pollution of soils with heavy metals appreciably increases the degree of metal differentiation, especially near the source of pollution. The parameter value decreases with increasing distance from the pollution source, probably due to the mechanical dilution of dust in the large soil volume.     

Is air-drying of soil samples an appropriate step in determining plant available potassium for corn?

Potassium (K) fertilizer recommendations are mainly based on air -dried soil samples which can lead to over- or under-estimation of plant available soil K. Three on-farm trials were conducted in North Dakota and Minnesota to determine the variation of soil test-K between air-dried (K_Dry) and field moist (K_Moist) soil samples. The differences between K_Dry and K_Moist decreased exponentially as soil K increased, but increased linearly with increasing soil moisture. Soil drying influenced the plant available soil K-test value, producing higher K values compared to the moist soil K. It is unclear based on these initial experiments which method might produce a more predictable K critical value to aid in directing K application for corn in this region.     

Soil properties,crop productivity and energetics under different tillage practices in fodder sorghum + cowpea – wheat cropping system

Tillage is an important agricultural operation which influences soil properties, crop yield and environment. Nine combinations of three tillage practices including conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT) were evaluated in fodder sorghum (Sorghum bicolor) + cowpea (Vigna unguiculata) – wheat (Triticum durum) cropping system for 5 years (2009–2014) on clay loam soil under limited irrigation. Continuous ZT practices significantly improved surface soil organic carbon, bulk density, infiltration rate and maximum water holding capacity. Carbon sequestration rate, soil organic carbon stock and soil enzymatic activities were relatively more under ZT than CT-CT practice. Higher fodder yield of sorghum + cowpea was recorded with CT (kharif) while wheat grain yield with ZT (rabi). However, the system productivity was statistically similar in all the tillage treatments on pooled data basis. The economic benefits were also maximum under ZT-ZT practice. The ZT-ZT practice recorded significantly lowest energy input (17.1 GJ ha^?1) which resulted in highest energy use efficiency (13.6) and energy productivity (518 kg GJ^?1). Thus, adoption of ZT significantly improved soil health, stabilized crop yield, increased profitability and energy use efficiency in the semi-arid agro-ecosystem.     

Silicon fertilization – A tool to boost up drought tolerance in wheat (Triticum aestivum L.) crop for better yield

In this study, impact of silicon (Si) application on wheat performance under drought stress is studied. Experimental soil was sandy clay loam with an average pH of 8.01, electrical conductivity (EC) of 2.36 dSm^?1, and calcium carbonate (CaCO₃) content of 2.16%. Soil was severely deficient in organic matter (<1%). Average extractable phosphorus (P) and potassium (K) concentration was 230 and 5.21 mg kg^?1, respectively. Silicon potassium metasilicate (K₂SiO₃) was applied at the rate of 0 and 12 kg/ha with three canal water irrigation frequencies including two, three, and four under randomized complete block design (RCBD) factorial fashion with three replications. Results indicated that drought stress significantly reduced plant height, spike length, shoot fresh weight, and number of spikelets/spike, eventually enhancing wheat yield. Concentration of K⁺ in shoot (28.65 mg g^?1) and grains (3.51 mg g^?1) increased with Si application, which helped to maintain water potential in plant even under reduced moisture level in plants and soil, ultimately producing more yield and biomass under drought stress conditions.     

Long–term effect of crop rotation and nutrient management on soil–plant nutrient cycling and nutrient budgeting in Indo–Gangetic plains of India

In the present investigation, the long-term effect of pulse crop inclusion in the maize-wheat rotation was assessed for the nutrient availability and soil-plant nutrient cycling under different nutrient management practices. Including pulses in the maize-wheat rotation improved soil organic carbon (SOC) and plant available macronutrients being higher in maize-wheat-mungbean rotation. Inclusion of mungbean to maize-wheat rotation enhanced the nitrogen (33.9%), phosphorus (46.4%), potassium (36.3%), and sulphur (55.5%) uptake in maize crop; likewise, alternate-year chickpea inclusion increased the uptake of these nutrients by 18.2, 19.1, 21.7, 32.1%, respectively. Inorganic fertilization maintained the positive annual balance of nitrogen, phosphorus, and zinc. By contrast, the nutrient balance under organic nutrient management was mostly negative. The magnitude of negative balance of potassium and sulphur was higher in inorganic than that of organic nutrient management. The low nutrient supply (particularly nitrogen) in organic fertilization largely inhibited the yield of cereal crops but not that of pulses. In view of this, the inclusion of pulses in the cereal-cereal systems could cause substantial improvement in soil fertility and sustainability in Indo-Gangetic plains. We infer that supply of nutrients like nitrogen and phosphorus in organic, and potassium and sulphur in recommended inorganic fertilization merit special attention.     

Crassula helmsii (T. Kirk) cockayne: Is it an aggressive alien aquatic plant in Britain?

The occurrence of this alien aquatic macrophyte has rapidly increased during the last decade reaching c. 100 sites mainly in England; these range from shallow acidic seasonal pools to small, more alkaline, nutrient-rich lakes. It is frequently dominant and can grow in an emergent form from 0·7m above the water to a submerged form 1·3m in length, to depths of c. 3m. Plant bimass is generally high with little seasonal cessation of growth. The habit is frequently a dense sward growth which smothers out other flora; it is present in c. ten reserves and is causing concern. It is widely available from aquatic suppliers, it has an enormous potential to propagate from small fragments and has a high growth rate. It is associated with soft sediments and possibly iron-rich areas; this is confirmed by growth trials in static water tanks. In flowing water trials, growth was even faster in water velocities up to 0·32 m s⁻¹, indicating its potential—although no river sites in Britain are yet known. Control by physical removal, often recommended, results in numerous propagules and should be combined with a secondary technique. This initial study suggests that this plant will remain a problem and caution is required to prevent its further spread. Studies of techniques for its control are needed.     

Effects of leguminous plant residues and NPK fertilizer application on the performance of yam (Dioscorea rotundata ‘c.v.’ ewuru) in south-western Nigeria

The effects of cultivating and incorporating residues of previous tropical kudzu (Pueraria phaseoloides) and soybean (Glycine max) with application of NPK fertilizer on yam performance were evaluated at the teaching and research farm, LAUTECH, Nigeria. There were nine treatments: incorporation of legume residues (5 t DM ha^?1), application of recommended fertilizer rate for yam (90–50–75 kg NPK ha^?1) in the zone or 50% of recommended rate (45–25–37.5 kg NPK ha^?1), alone and in combination with residues and a control without residues or fertilizer in a randomized complete block design. Cultivation of previous legumes reduced soil nematode population (>200%) compared with no legumes. For both years, application of Pueraria residues improved tuber yield by an average of 15.8% compared with control. Fertilizer application enhanced arbuscular mycorrhizal (AM) colonization of yam roots but AM colonization was lower (～50%) in plots where Pueraria residues were incorporated compared with other plots. Combined application of plant residues with fertilizer improved soil organic carbon, total N, exchangeable Ca and Mg compared with application of NPK fertilizer. From these results, it is concluded that half of the recommended NPK rate may be adequate and incorporation of residues with reduced NPK fertilizer application may be a sustainable soil fertility management option for continuous yam production.